fix(web): resolve DOM nesting warnings and broken doc links

[prakharsingh-74]

Concisely describe the change

This PR resolves runtime console errors across the podman.io website and broken relative documentation paths.

Key Changes:

• Resolve DOM Nesting Warnings: Changed parent <p> wrappers to <div> elements in CustomCard.tsx and NotFound.tsx to fix invalid nesting violations (e.g. block-level Markdown elements/divs rendering inside paragraph tags).

• Fix Unique Key Warning: Added key={idx} to the options.map iteration block inside the CommunityMeetingsCardGrid dropdown renderer to satisfy React list uniqueness requirements.

• Fix Relative Docs Paths: Corrected broken relative documentation links in docs/index.md pointing to docs/installation and docs/checkpoint. They now correctly resolve relative to /docs (i.e. ./installation and ./checkpoint).

Before fix

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After fix

Checklist

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• Referenced issues using Fixes: #00000 in commit message (if applicable)
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